Be holy! - the categorical imperative.  

I used to think that quietism was the same as holiness; something to do with a person's aura - an appearance of detachment from things that work against the soul. But quietism itself is not holiness, even if some holy people cultivate a quiet spirit after learning that this is what pleases God. Essentially, they have learned to put God first and devote themselves to him - which is holiness. The Old Testament priests were 'holy to the Lord' because they were devoted exclusively to His worship and service. Holiness is often construed negatively as 'separation from' sin and while God's holiness is indeed his separation from sin, it is foremost the mutual devotion of the three persons of the Trinity to one another. God's devotion to himself. This means that separation from sin is inherent in his nature because out of which flows in the personal, eternal, unchangeable and perfect love - the love of the Father, Son and Holy Spirit for one another. Their consummate mutual devotion is such that no darkness can exist in the context of pure light.

Out of God's consummate holiness comes the categorical imperative 'be holy!' The simple rationale is 'be holy, for I the Lord your God am holy.' Be like me! It is impossible for us to be like him ontologically and morally for we are creaturely and sinful, always doing battle with a heart that is deceitful and desperately wicked, a world that has turned its back on the Creator, a body which is so often the vehicle of sin and a Devil who is the enemy of our souls. First-century Christians in Pontus, Galatia, Cappadocia, Asia and Bythinia found the going hard. Their Christian profession seemed to work against them in an unbelieving and often hostile life-setting.

Yet the categorical imperative came to them as to us: 'Be holy, for I, the lord your God am holy.' As Christians we are committed to warring, a striving, following,  learning and persevering - to being 'transformed by the renewing of our mind, that we may prove what is that good, and acceptable, and perfect, will of God.' (Rom 12:2) Is that a forlorn hope? Far from it! Augustine, who understood something about the nature of divine grace learned to pray 'give what you command and command what you will.' Paul writes 'Therefore, my beloved ... work out your own salvation with fear and trembling, for it is God who works in you to will and do his own pleasure.' (Phil 2:12ff)